Which Statement Best Describes the Basic Premise of the Cross-Sectional

Which statement best describes the basic premise of the cross-sectional research design?

A) Assess different age groups (e.g. ,5-,10-,15-year-olds) at the same time (e.g. ,during the same week)
B) Assess the same age group (e.g. ,only 5-year-olds) at the same time (e.g. ,during the same week)
C) Assess different age groups (e.g. ,5-,10-,15-year-olds) at different times (e.g. ,5-year-olds in 2003,10-year-olds in 2004,and 15-year-olds in 2005)
D) Assess the same group (e.g. ,5-year-olds) at different times (e.g. ,first test when kids are 5,then when they are 10,and finally when they turn 15)